Ceramic resistor and preparation method thereof

Abstract

The invention discloses a ceramic resistor and a preparation method thereof, and the preparation method of the ceramic resistor comprises the following steps: obtaining a ceramic raw material according to a preset material ratio, and pretreating the ceramic raw material; firing the pretreated ceramic raw material to obtain a first ceramic resistor rod and a second ceramic resistor rod; metal coatings with preset lengths are sprayed at the two ends of the first ceramic resistor rod and the second ceramic resistor rod respectively, and insulating coatings are arranged on the outer circular surfaces; a first electrode and a second electrode are welded to the two ends of the first ceramic resistance rod through an electric induction heating method, and a first resistance rod is obtained; welding a third electrode and a fourth electrode at two ends of the second ceramic resistance rod to obtain a second resistance rod; the first resistor rod and the second resistor rod are connected in series based on the internal thread and the external thread to obtain the ceramic resistor, and the working medium of the ceramic resistor is No.45 transformer oil. The ceramic resistor prepared by the invention can keep a stable resistance value in a high-temperature and high-pressure environment, and the stability of a circuit is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic components, in particular to a ceramic resistor and a preparation method thereof. BACKGROUND

[0002] Resistor elements include carbon film resistors, metal film resistors, metal wire wound resistors, metal resistor chips, etc., and are suitable for different circuits in different industries such as electronics and electric power. Among them, high-power resistors are mostly wire wound resistors, which are used in circuits that need to discharge large pulse energy in a short time, such as capacitor charging and discharging circuit resistors, power supply neutral point grounding resistors, RC overvoltage absorption circuit resistors, transformer current limiting starting resistors, motor current limiting starting resistors, etc. However, due to the large size of wire wound resistors, it is difficult to miniaturize, and it must be fixed by welding or other methods when used in high-voltage and high-energy environments, resulting in high process difficulty and poor reliability. In addition, wire wound resistors cannot be inductive, so they cannot be used in high-frequency circuits.

[0003] Zinc oxide chips can be used for high-voltage and high-energy absorption, but as resistor elements, zinc oxide chips have poor stability at high voltage and are nonlinear resistors, which cannot meet the requirement of stable resistance. In addition, in high-voltage and high-frequency circuit operation, the working medium of 45# transformer oil or SF6 gas is easy to react physically or chemically with the resistor body, making it difficult to maintain stable operation of the high-voltage and high-frequency circuit, and cannot meet the requirement of stable resistance, resulting in degradation of resistor performance, and even causing circuit failure.

[0004] Therefore, there is an urgent need for a resistor element to solve the problem of large size and poor high-frequency characteristics of resistor elements in the prior art when used in high-voltage and high-energy environments. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides a ceramic resistor and a preparation method thereof, aiming to provide a resistor element with stable resistance suitable for high-voltage and high-frequency circuits.

[0006] The present application discloses a preparation method of a ceramic resistor, comprising:

[0007] Obtain ceramic raw materials according to a predetermined material ratio, and pretreat the ceramic raw materials;

[0008] Fire the pretreated ceramic raw materials to obtain a first ceramic resistor rod and a second ceramic resistor rod;

[0009] Spray a metal coating of a predetermined length on both ends of the first ceramic resistor rod and the second ceramic resistor rod, respectively, and set an insulating coating on the outer cylindrical surface of the first ceramic resistor rod and the second ceramic resistor rod, respectively;

[0010] The first electrode and the second electrode are welded on both ends of the first ceramic resistance rod by an electric induction heating method to obtain the first resistance rod; and the third electrode and the fourth electrode are welded on both ends of the second ceramic resistance rod by the electric induction heating method to obtain the second resistance rod; the second electrode is provided with external threads, and the third electrode is provided with internal threads;

[0011] The first resistance rod and the second resistance rod are connected in series based on the internal threads and the external threads to obtain the ceramic resistor, and a working medium of the ceramic resistor is No. 45 transformer oil.

[0012] Preferably, the ceramic raw material is obtained according to a preset material ratio, including:

[0013] The first proportion of bentonite, the second proportion of aluminum oxide powder, the third proportion of mullite powder and the fourth proportion of graphite powder are obtained;

[0014] The first proportion is in a range of 30% to 55% of the total mass of the ceramic raw material, the second proportion is in a range of 40% to 60% of the total mass of the ceramic raw material, the third proportion is in a range of 5% to 15% of the total mass of the ceramic raw material, and the fourth proportion is in a range of 1% to 5% of the total mass of the ceramic raw material.

[0015] Preferably, the pretreatment of the ceramic raw material includes:

[0016] The bentonite is calcined in a calcining furnace at a first preset temperature for 5 to 7 hours to remove water and impurities in the bentonite, and the first preset temperature is in a range of 850 degrees Celsius to 950 degrees Celsius;

[0017] Zirconium oxide grinding balls are added to the calcined bentonite and placed in a closed ball mill for grinding to obtain bentonite particles, and the weight ratio of the bentonite to the zirconium oxide grinding balls is 2:1;

[0018] The graphite powder is placed in an oven and dried at a second preset temperature for 2 to 4 hours, and the second preset temperature is in a range of 110 degrees Celsius to 150 degrees Celsius;

[0019] The bentonite particles, the dried graphite powder, the aluminum oxide powder and the mullite powder are put into the closed ball mill for dry mixing to obtain the raw material powder.

[0020] Preferably, the pretreated ceramic raw material is fired to obtain the first ceramic resistance rod and the second ceramic resistance rod, including:

[0021] Deionized water, an adhesive and a dispersant are sequentially added to the raw material powder, and the mixture is stirred to form a slurry, and the slurry is prepared into granulated material by a spray granulation device;

[0022] The granulation material is prepared into a green body by dry pressing or isostatic pressing, and the green body is placed in an oven for baking at a third preset temperature in the range of 105 DEG C. to 125 DEG C.

[0023] The baked green body is placed in a crucible, and the crucible is placed in a sintering furnace for sintering at a fourth preset temperature in the range of 1200 DEG C. to 1400 DEG C. for 6 to 8 hours and then cooling treatment, to obtain a ceramic primary body; the sintering furnace is filled with inert gas or is in a vacuum state;

[0024] The ceramic primary body is subjected to finish machining and end face treatment to obtain a first ceramic resistance rod and a second ceramic resistance rod.

[0025] Preferably, an insulating coating is arranged on the outer circumferential surface of the first ceramic resistance rod and the second ceramic resistance rod, comprising:

[0026] The insulating material is filled in the outer circumferential surface of the first ceramic resistance rod and the second ceramic resistance rod by vacuum pouring by using a mold tool; the insulating material comprises at least one of dielectric paint, epoxy encapsulating material or polyurethane glue;

[0027] The insulating material is solidified to obtain the insulating coating.

[0028] Preferably, the metal coating and the metal electrode are in clearance fit, and the one-side clearance is 0.1 mm; the metal electrode comprises a first electrode, a second electrode, a third electrode and a fourth electrode;

[0029] The clearance between the metal coating and the metal electrode is filled with conductive auxiliary material, and the conductive auxiliary material comprises conductive solder paste.

[0030] The application further discloses a ceramic resistor prepared based on the preparation method of the ceramic resistor.

[0031] The first resistance rod comprises a first ceramic resistance rod, and two ends of the first ceramic resistance rod are connected with the first electrode and the second electrode, respectively.

[0032] The second resistance rod comprises a second ceramic resistance rod, and two ends of the second ceramic resistance rod are connected with the third electrode and the fourth electrode, respectively.

[0033] The second electrode and the third electrode are threadedly connected to connect the first resistance rod and the second resistance rod in series, to form the ceramic resistor, and the working medium of the ceramic resistor is No. 45 transformer oil.

[0034] Preferably, the surface of the second electrode is provided with external threads, the third electrode is provided with internal threads matched with the external threads, and the first resistance rod is connected with the second resistance rod in series through the external threads and the internal threads.

[0035] Preferably, the two ends of the first ceramic resistance rod are respectively provided with metal coatings, and the first electrode and the second electrode are welded with the first ceramic resistance rod based on the metal coatings.

[0036] The two ends of the second ceramic resistance rod are respectively provided with metal coatings, and the third electrode and the fourth electrode are welded with the second ceramic resistance rod based on the metal coatings.

[0037] Preferably, the outer circumferential surfaces of the first ceramic resistance rod and the second ceramic resistance rod are respectively provided with insulating coatings.

[0038] Compared with the prior art, the ceramic resistor and the preparation method thereof provided by the present application have the following beneficial effects: the ceramic resistor and the preparation method thereof provided by the present application solve the problems of the resistor element in the prior art, such as too large volume and poor high-frequency characteristics, in the use of high-voltage and high-energy environment. Through specific ceramic raw material ratio and preparation process, the ceramic resistor obtained has stable resistance value and is suitable for high-voltage and high-frequency lines. In addition, the structure of the ceramic resistor is reasonably designed, the two ceramic resistance rods are connected in series through the threaded connection, which not only improves the stability and reliability of the resistor, but also facilitates installation and maintenance. At the same time, the setting of the insulating coating and the metal coating further enhances the insulation performance and the conductivity of the resistor, and improves the overall performance of the resistor. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 A flowchart of the preparation method of the ceramic resistor provided by the present application is shown in the figure.

[0040] Figure 2 A structure diagram of the ceramic resistor provided by the present application is shown in the figure.

[0041] Figure 3 A structure diagram of the ceramic resistance rod provided by the present application is shown in the figure.

[0042] REFERENCE NUMERALS

[0043] 1, first resistance rod; 2, second resistance rod; 3, first ceramic resistance rod; 4, first electrode; 5, second electrode; 6, second ceramic resistance rod; 7, third electrode; 8, fourth electrode; 9, insulating coating. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0045] The present application will be further described in detail below in combination with the drawings.

[0046] As Figure 1 shown, the embodiment of the present application provides a preparation method of ceramic resistor, comprising the following steps.

[0047] S1, according to the preset material ratio, ceramic raw materials are obtained, and the ceramic raw materials are pretreated.

[0048] In the embodiment of the present application, the ceramic raw materials include bentonite, alumina powder, mullite powder and graphite powder. Among them, bentonite, alumina powder and mullite powder are used to form porous ceramic material, and the porous ceramic material is used as the matrix, which has good thermal shock resistance. Graphite powder is used as conductive material with stable physical and chemical properties.

[0049] According to the preset material ratio, the process of obtaining ceramic raw materials includes obtaining a first proportion of bentonite, a second proportion of alumina powder, a third proportion of mullite powder and a fourth proportion of graphite powder, wherein the first proportion is in the range of 30% to 55% of the total mass of the ceramic raw materials, the second proportion is in the range of 40% to 60% of the total mass of the ceramic raw materials, the third proportion is in the range of 5% to 15% of the total mass of the ceramic raw materials, and the fourth proportion is in the range of 1% to 5% of the total mass of the ceramic raw materials.

[0050] The ceramic resistor made of the ceramic raw materials and the ratio in the embodiment of the present application has the inductance-free characteristic of the resistor itself, higher use temperature, can withstand greater impact current, and can work in high voltage and high frequency lines.

[0051] In the embodiment of the present application, the ceramic raw materials need to be pretreated first, and the pretreatment includes the following steps:

[0052] S11, the bentonite is calcined in the calcining furnace according to the first preset temperature for 5 to 7 hours to remove the water and impurities in the bentonite, and the first preset temperature is in the range of 850 degrees Celsius to 950 degrees Celsius.

[0053] S12, zirconium oxide grinding balls are added to the calcined bentonite and placed in a closed ball mill for grinding to obtain bentonite particles, and the weight ratio of bentonite to zirconium oxide grinding balls is 2:1.

[0054] S13, the graphite powder is placed in an oven and dried at a second preset temperature for 2 to 4 hours, and the second preset temperature is in the range of 110 degrees Celsius to 150 degrees Celsius.

[0055] S14, the bentonite particles, the dried graphite powder, the alumina powder and the mullite powder are put into the closed ball mill for dry mixing to obtain the raw material powder.

[0056] In this way, the pretreated ceramic raw material is more delicate and uniform, which is beneficial to improve the performance of the ceramic resistance rod prepared subsequently.

[0057] S2, firing the pretreated ceramic raw material to obtain a first ceramic resistance rod and a second ceramic resistance rod.

[0058] In the embodiment of the present application, the pretreated ceramic raw material is fired to obtain a ceramic resistance rod. Specifically, the firing process comprises the following steps:

[0059] S21, adding deionized water, a binder and a dispersant into the raw material powder in sequence and stirring to prepare a slurry, and preparing the slurry into granulated material by a spray granulation device.

[0060] S22, preparing the granulated material into a green body by dry pressing or isostatic pressing, and placing the green body in an oven for baking at a third preset temperature in the range of 105 to 125 degrees Celsius.

[0061] S23, placing the baked green body in a crucible, and placing the crucible in a sintering furnace for sintering at a fourth preset temperature for 6 to 8 hours and then cooling treatment to obtain a ceramic primary body.

[0062] The fourth preset temperature is in the range of 1200 to 1400 degrees Celsius, and the sintering furnace is filled with inert gas or is in a vacuum state.

[0063] S24, finishing the end face of the ceramic primary body to obtain a first ceramic resistance rod and a second ceramic resistance rod.

[0064] The firing method of the first ceramic resistance rod and the second ceramic resistance rod will be described in detail below through a specific example.

[0065] First, the bentonite is calcined at 850 to 950 degrees Celsius in a muffle furnace for 6 hours to remove the water and impurities inside, and the water loss rate is 14 to 19%. Then, the calcined bentonite and zirconia grinding balls are placed in a sealed ball mill in a weight ratio of 2:1 for crushing, the crushing speed is 51.5 Hz, and the crushing time is 16 hours to obtain a suitable particle size in the range of 8.5 to 9.2 microns.

[0066] Then, 5000g of bentonite, 4500g of alumina powder, 500g of mullite powder, and 200g of graphite powder are weighed; the bentonite and the graphite powder are first dried in an oven at 110-150℃ for 2-4h, and then the 5200g of the premix and 8600g of zirconium oxide grinding balls are dry-mixed in a closed ball mill, 5600g of D20 zirconium oxide grinding balls and 3000g of D10 zirconium oxide grinding balls are used, the crushing speed and time are 51.5Hz and 4-6h; then the alumina powder and the mullite powder are added into the closed ball mill for dry mixing, the crushing speed and time are 51.5Hz and 12-24h to obtain the uniformly mixed powder with a weight of 10200g.

[0067] Then, deionized water, a binder, and a dispersant are added into the uniformly mixed powder, 2550ml of deionized water, 1530ml of the binder, and 357ml of the dispersant are used to prepare a slurry in a closed stirring barrel, the stirring speed and time are 20-25Hz and 4-6h, and the slurry is prepared into granules with a certain particle size range by a spray granulation device. According to requirements, dry pressing, isostatic pressing, or other forming methods are selected to form the green body, the forming pressure is 100-110MPa per unit area, and the green body is dried in an oven at 105-125℃.

[0068] Further, the green body is placed in a crucible, the adjacent green bodies are separated by graphite paper or graphite pads, the crucible is placed in a sintering furnace, a vacuum or an inert gas is used to form a protective atmosphere, the heating rate is controlled to be 2-8℃ / min, high-temperature sintering is performed at 1200-1400℃ for 6-8h, then the furnace is cooled, and the end face is processed by finishing to obtain the first ceramic resistance rod and the second ceramic resistance rod.

[0069] The first ceramic resistance rod and the second ceramic resistance rod prepared in this way have high resistance performance and stability.

[0070] S3, a metal coating layer with a preset length is sprayed on each end of the first ceramic resistance rod and the second ceramic resistance rod, and an insulating coating layer is arranged on the outer circumferential surface of the first ceramic resistance rod and the second ceramic resistance rod.

[0071] In the embodiment of the present application, the ceramic resistance rod itself is made of ceramic material, and the resistance value cannot be directly tested. According to technical requirements, a metal coating layer with a certain length range is arranged at both ends of the ceramic resistance rod as an electrode to test the resistance value.

[0072] Specifically, the metal coating layer can be made of aluminum material or copper material or other materials with good conductivity to provide current-carrying capacity and withstand large instantaneous current. The metal coating layer is sprayed on both ends of the first ceramic resistance rod and the second ceramic resistance rod by arc spraying, thermal spraying, plasma spraying, or the like. The metal coating layer is sprayed in an inert gas atmosphere such as argon.

[0073] The metal coating is an electrically conductive aid, which is sprayed on the ceramic resistance rod at the circumferential area close to the end, and the axial length is 18-25 mm. The metal coating at both ends of the ceramic resistance rod is of the same length, accounting for 18.4%-25.6% of the length of the resistance rod.

[0074] Further, in order to improve the insulation performance of the ceramic resistance rod, an insulating coating is also needed to be arranged on the outer circumferential surface thereof. Specifically, the insulating material is filled in the outer circumferential surface of the first ceramic resistance rod and the second ceramic resistance rod in a vacuum potting manner by using a mold tool, and the insulating material is solidified to obtain the insulating coating. The insulating material includes at least one of dielectric paint, epoxy encapsulating material or polyurethane glue.

[0075] S4, welding the first electrode and the second electrode at both ends of the first ceramic resistance rod by the electric induction heating method to obtain the first resistance rod, and welding the third electrode and the fourth electrode at both ends of the second ceramic resistance rod by the electric induction heating method to obtain the second resistance rod.

[0076] In the embodiment of the present application, in order to improve the connection strength between the ceramic resistance rod and the electrode, the electric induction heating method is used for welding. Specifically, the first electrode and the second electrode are welded at both ends of the first ceramic resistance rod by using the electric induction heating equipment to obtain the first resistance rod. At the same time, the third electrode and the fourth electrode are welded at both ends of the second ceramic resistance rod to obtain the second resistance rod. The metal coating and the metal electrode are in clearance fit, and the single-side clearance is 0.1 mm. The metal electrode is the first electrode, the second electrode, the third electrode and the fourth electrode. The gap between the metal coating and the metal electrode is filled with conductive aid material, and the conductive aid material includes conductive solder paste.

[0077] In the embodiment of the present application, the welding position of the first ceramic resistance rod and the first electrode and the second electrode is provided with an insulating coating, and the welding position of the second ceramic resistance rod and the third electrode and the fourth electrode is provided with an insulating coating. The second electrode is provided with an external thread, and the third electrode is provided with an internal thread matched with the external thread, so as to facilitate the subsequent series connection of the first resistance rod and the second resistance rod.

[0078] S5, series connecting the first resistance rod and the second resistance rod based on the internal thread and the external thread to obtain the ceramic resistor.

[0079] As Figure 2 and Figure 2As shown, the embodiment of the present application further provides a ceramic resistor prepared based on the preparation method of the ceramic resistor. The ceramic resistor comprises a first resistor rod 1 and a second resistor rod 2. The first resistor rod 1 comprises a first ceramic resistor rod 3, and two ends of the first ceramic resistor rod 3 are connected with a first electrode 4 and a second electrode 5 respectively. The second resistor rod 2 comprises a second ceramic resistor rod 6, and two ends of the second ceramic resistor rod 6 are connected with a third electrode 7 and a fourth electrode 8 respectively. The second electrode 5 is threadedly connected with the third electrode 7, so that the first resistor rod 1 and the second resistor rod 2 are connected in series to form the ceramic resistor, and the working medium of the ceramic resistor is No. 45 transformer oil.

[0080] In the embodiment of the present application, the surface of the second electrode 5 is provided with external threads, the third electrode 7 is provided with internal threads matched with the external threads, and the first resistor rod 1 is connected in series with the second resistor rod 2 through the external threads and the internal threads.

[0081] In the embodiment of the present application, the two ends of the first ceramic resistor rod 3 are respectively provided with metal coatings, and the first electrode 4 and the second electrode 5 are welded with the first ceramic resistor rod 3 based on the metal coatings. The two ends of the second ceramic resistor rod 6 are respectively provided with metal coatings, and the third electrode 7 and the fourth electrode 8 are welded with the second ceramic resistor rod 6 based on the metal coatings. The outer circumferential surfaces of the first ceramic resistor rod 3 and the second ceramic resistor rod 6 are respectively provided with insulating coatings 9.

[0082] The ceramic resistor and the preparation method thereof provided by the embodiment of the present application have the advantages of stable resistance and being suitable for high-voltage and high-frequency lines. The performance of the ceramic resistor disclosed by the present application is verified by specific tests as follows.

[0083] Example 1: Three ceramic resistors with the outer dimensions of D30xL190mm are prepared, polyurethane glue, epoxy encapsulating material and dielectric coating are respectively coated on the outer circumferential surfaces of the three ceramic resistors, and No. 45 transformer oil is immersed at a preset ambient temperature, and the resistance change from 180 to 200 days is recorded. It is verified that the resistance change rate of the ceramic resistor corresponding to the polyurethane glue from 180 to 200 days is 0.85% to 0.92%, the resistance change rate of the ceramic resistor corresponding to the epoxy encapsulating material from 180 to 200 days is 3.9% to 18.1%, and the resistance change rate of the ceramic resistor corresponding to the dielectric coating from 180 to 200 days is 1.1% to 5.76%. It can be seen that under the same conditions, the performance of the ceramic resistor corresponding to the polyurethane glue is the best.

[0084] Example 2, a ceramic resistor with a size of D30xL45mm is prepared and immersed in No. 45 transformer oil, 42kV, 46kV, 50kV, 56kV and 60kV impulse voltages are applied to both ends of the ceramic resistor for 20 times successively, and the ceramic resistor has no breakdown, flashover or cracking phenomenon, the resistance change rate of the ceramic resistor during the test is-21.74%-37.94%, and the cold resistance change rate after the test is-10%.

[0085] Example 3, a ceramic resistor with a size of D30xL45mm is prepared and immersed in No. 45 transformer oil, 56kV impulse voltage is applied to both ends of the ceramic resistor for 120 times successively, and the ceramic resistor has no breakdown, flashover or cracking phenomenon, the resistance change rate of the ceramic resistor during the test is-33.96%-36.79%, and the cold resistance change rate after the test is-14.03%.

[0086] Example 4, a ceramic resistor with a size of D30xL45mm is prepared and immersed in No. 45 transformer oil, 56kV impulse voltage is applied to both ends of the ceramic resistor for 15 times successively, and the ceramic resistor has no breakdown, flashover or cracking phenomenon, the resistance change rate of the ceramic resistor during the test is-33.55%-37.23%, and the cold resistance change rate after the test is-1% compared with that in Example 3.

[0087] Example 5, a ceramic resistor with a size of D30xL35mm is prepared and immersed in No. 45 transformer oil, 46kV, 50kV, 56kV and 60kV impulse voltages are applied for 3 times for each voltage, the real-time voltage value and current value under high-voltage impulse are recorded, and the resistance value under high-voltage impulse is obtained; the voltage coefficient of the ceramic resistor is-0.03--1.42% / kV.cm, and the ceramic resistor has no breakdown, flashover or cracking phenomenon.

[0088] It can be known from the above technical solution that the ceramic resistor and the preparation method thereof provided by the application solve the problems of too large volume and poor high-frequency characteristics of the resistor element in the prior art when used in a high-voltage and high-energy environment. Through specific ceramic raw material proportioning and preparation process, the ceramic resistor obtained has stable resistance and is suitable for high-voltage and high-frequency lines. In addition, the structure of the ceramic resistor is reasonably designed, two ceramic resistor rods are connected in series through a threaded connection, which not only improves the stability and reliability of the resistor, but also facilitates installation and maintenance. At the same time, the setting of the insulating coating and the metal coating further enhances the insulation performance and the conductive performance of the resistor, and improves the overall performance of the resistor.

[0089] The above merely describes the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a ceramic resistor, characterized in that, include: Ceramic raw materials are obtained according to a preset material ratio, and the ceramic raw materials are pretreated. The pretreated ceramic raw materials are fired to obtain a first ceramic resistance rod and a second ceramic resistance rod. A metal coating of a predetermined length is sprayed onto both ends of the first ceramic resistor rod and the second ceramic resistor rod, and an insulating coating is provided on the outer circumference of the first ceramic resistor rod and the second ceramic resistor rod, respectively. A first resistance rod is obtained by welding a first electrode and a second electrode to both ends of the first ceramic resistance rod using an induction heating method; and a second resistance rod is obtained by welding a third electrode and a fourth electrode to both ends of the second ceramic resistance rod using an induction heating method; the second electrode is provided with an external thread, and the third electrode is provided with an internal thread. By connecting the first resistance rod and the second resistance rod in series based on the internal thread and the external thread, a ceramic resistor is obtained. The working medium of the ceramic resistor is No. 45 transformer oil.

2. The method for preparing a ceramic resistor according to claim 1, characterized in that, The process of obtaining ceramic raw materials according to a preset material ratio includes: Obtain bentonite in a first proportion, alumina powder in a second proportion, mullite powder in a third proportion, and graphite powder in a fourth proportion. The first proportion ranges from 30% to 55% of the total mass of ceramic raw materials, the second proportion ranges from 40% to 60% of the total mass of ceramic raw materials, the third proportion ranges from 5% to 15% of the total mass of ceramic raw materials, and the fourth proportion ranges from 1% to 5% of the total mass of ceramic raw materials.

3. The method for preparing a ceramic resistor according to claim 2, characterized in that, The pretreatment of ceramic raw materials includes: The bentonite is calcined in a calcining furnace at a first preset temperature for 5 to 7 hours to remove moisture and impurities from the bentonite. The first preset temperature ranges from 850 degrees Celsius to 950 degrees Celsius. Zirconia grinding balls are added to the calcined bentonite and ground in a closed ball mill to obtain bentonite particles. The weight ratio of the bentonite to the zirconia grinding balls is 2:

1. The graphite powder is placed in an oven and dried at a second preset temperature for 2 to 4 hours, the second preset temperature being in the range of 110 degrees Celsius to 150 degrees Celsius. The bentonite particles, the dried graphite powder, the alumina powder, and the mullite powder are placed in a closed ball mill and dry-mixed to obtain raw material powder.

4. The method for preparing a ceramic resistor according to claim 3, characterized in that, The ceramic raw material after the firing pretreatment is used to obtain a first ceramic resistance rod and a second ceramic resistance rod, including: Deionized water, binder and dispersant are added sequentially to the raw material powder and stirred to form a slurry. The slurry is then granulated using a spray granulation device. The granulated material is prepared into a green body by dry pressing or isostatic pressing, and the green body is placed in an oven and baked at a third preset temperature, the third preset temperature being between 105 degrees Celsius and 125 degrees Celsius. The baked green body is placed in a crucible, and the crucible is placed in a sintering furnace and sintered at a fourth preset temperature for 6 to 8 hours, and then cooled to obtain a ceramic precursor; the fourth preset temperature ranges from 1200 degrees Celsius to 1400 degrees Celsius, and the sintering furnace is filled with inert gas or the sintering furnace is in a vacuum state. The ceramic substrate is subjected to fine-machining end face treatment to obtain the first ceramic resistance rod and the second ceramic resistance rod.

5. The method for preparing a ceramic resistor according to claim 1, characterized in that, The step of setting an insulating coating on the outer circumferential surfaces of the first ceramic resistance rod and the second ceramic resistance rod respectively includes: Using a mold tooling, insulating material is filled into the outer circular surfaces of the first ceramic resistance rod and the second ceramic resistance rod by vacuum potting; the insulating material includes at least one of dielectric coating, epoxy encapsulant or polyurethane adhesive. The insulating material is cured to obtain the insulating coating.

6. The method for preparing a ceramic resistor according to claim 1, characterized in that, The metal coating and the metal electrode are fitted with a gap, with a gap of 0.1 mm on one side. The metal electrode includes the first electrode, the second electrode, the third electrode, and the fourth electrode. The gap between the metal coating and the metal electrode is filled with a conductive additive material, which includes conductive solder paste.

7. A ceramic resistor, characterized in that, The ceramic resistor is prepared according to the method for preparing a ceramic resistor as described in any one of claims 1 to 6, wherein the ceramic resistor comprises: a first resistance rod and a second resistance rod; The first resistance rod includes a first ceramic resistance rod, and the two ends of the first ceramic resistance rod are respectively connected to a first electrode and a second electrode. The second resistance rod includes a second ceramic resistance rod, and the two ends of the second ceramic resistance rod are respectively connected to the third electrode and the fourth electrode; The second electrode is threadedly connected to the third electrode so that the first resistance rod and the second resistance rod are connected in series to form a ceramic resistor. The working medium of the ceramic resistor is No. 45 transformer oil.

8. The ceramic resistor according to claim 7, characterized in that, The surface of the second electrode is provided with an external thread, and the third electrode is provided with an internal thread that matches the external thread. The first resistance rod is connected in series with the second resistance rod through the external thread and the internal thread.

9. The ceramic resistor according to claim 8, characterized in that, The first ceramic resistance rod has metal coatings at both ends, and the first electrode and the second electrode are welded to the first ceramic resistance rod based on the metal coatings. The second ceramic resistance rod has metal coatings at both ends, and the third electrode and the fourth electrode are welded to the second ceramic resistance rod based on the metal coatings.

10. The ceramic resistor according to claim 1, characterized in that, Both the first ceramic resistor rod and the second ceramic resistor rod have an insulating coating on their outer circular surfaces.

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